DNA carries genetic information and is found in chromosomes, mitochondria, and chloroplasts. It is a double-stranded polymer made up of deoxyribonucleotides with a sugar-phosphate backbone and nitrogenous bases that pair through hydrogen bonding. Genes composed of DNA are located on chromosomes in the cell nucleus, and the DNA is packaged through coiling around histone proteins into chromatin and condensed further into chromosomes.

1. DNA
CHROMOSOMES,GENES
PRESENTED BY MAHLATSE
KHULWANA
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4. DNA
 DNA-Deoxyribonucleic acid
 DNA is a polymer of deoxyribonucleotides
 The structure of DNA is doble stranded
 It is a double helix
 Found in chromosomes ,mitochondria and chloroplasts
 Carries genetic information
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5. LOCATION OF DNA IN A CELL
 Chromatin is a complex DNA and protein and is
found in the nucleus eukaryotic cells.
 Histones are proteins that are responsible for the first
level of DNA packing in chromatin
 The chromatin network in the nucleus of a cell will coil
up tightly during cell division and form individual
chromosomes
 Chromosomes are always duplicated during this
process, a duplicate chromosome consist of 2
chromatids attached to each other by a centromere
 Each chromosome consist of several genes which
consist of 2 long DNA strand.
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6. Structure of DNA
DNA molecules are polymers called polynucleotides-each
polynucleotide is made up of monomers called Nucleotides
Each nucleotide consist of
A nitrogenous base(Adenine, Thymine, Cytosine, Guanine)
A 5-carbon sugar called deoxyribose
A phosphate group

7. DNA NUCLEOTIDE
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8. NITROGENOUS BASES OF DNA
 Nitrogenous bases of DNA are divided into two groups
 Purines and pyrimidines
 Purines(Made of a 6 member ring , fused to a 5 member ring)
 Adenine
 Guanine
 Pyrimidines(Made of one 6 member ring)
 Thymine
 Cytosine

9. PURINES
AND
PYRIMIDINES
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10. Complementary pairing
 Bases pair with other complementary bases
 Purines with two carbon rings pair only with single pyrimidines
 A+T
 G+C
 Complementary pairing is important for the uses and storage of the genetic
information.
 Interaction is stabilized by hydrogen bonds

11. DNA and hydrogen
bonding
 Hydrogen bond-A chemical bond in which a
hydrogen atom of one molecule is attracted to an
electronegative atom, especially a nitrogen ,
oxygen or fluorine atom, usually of another
molecule
 The electronegativity atom with the lone pair
electrons is called the hydrogen bond Acceptor
 The electronegativity atom bonded to the
hydrogen is called hydrogen bond Donor
 The hydrogen bond donor must be aligned 180
degrees to the hydrogen bond acceptor
This Photo by Unknown Author is licensed under CC BY-SA
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12. Double helix
structure of
DNA

13. Role of DNA
 DNA is vital for all living beings – even plants.
 It is important for:
 inheritance,
 coding for proteins and
 the genetic instruction guide for life and its processes.
 DNA holds the instructions for an organism's or each cell’s development and
reproduction and ultimately death.
 DNA can replicate itself

14. These are pictures of my own DNA extracted from my saliva and cheeks in an experiment.

15. REFERENCES
 Chhabra,N.(2020).’DNA(Deoxyribonucleic acid)structure and functions’.Available from
slideshare@https://www.slideshare.net/namarta28/dna-deoxyribonucleic-acid-structure-
and-functions-237585570,(Accessed :16 August 2020)
 Jakan,V.(2020).’DNA,CHROMOSOMES & GENES’.Available from slideshare@
https://www.slideshare.net/jagan6/dna-chromosomes-genes-237711416 ,(Accessed:16
august 2020)
 Dev,H.(2014).’Structure of DNA & RNA’.Available from
slideshare@https://www.slideshare.net/Himanshudev1/structure-of-dna-and-rna ,(Accessed
18 august 2020).
 Chhabra,N.(2012).’DNA structure,Functions and Properties’.Available from slideshare
@https://www.slideshare.net/namarta28/dna-structure-and-properties ,(Accessed 18 August
2020).
 Molashok,S.(2019).’Structure of dna’.Available from
slideshare@https://www.slideshare.net/shirsathamolashok/structure-of-dna-
165081795,(Accessed 18 August 2020).
 https://drive.google.com/drive/folders/19-
mIeXOfu538WVLSBqYMc4DnDuyEq0YD?usp=sharing

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